Halle Berry's Movie Was the Last Straw in Custody Battle, Says Source

Halle Berry's latest movie was supposed to be the big-budget romantic comedy New Year's Eve – but for the actress and her ex, Gabriel Aubry, the feel-good film may have been the final straw in their already-strained custody arrangement over their 2 ½-year-old daughter Nahla.

According to a source close to Berry, the actress's movie contract included compensation for Aubry to accompany her and Nahla to New York City for about two weeks of filming. But when Aubry decided not to go, says the source, Berry was forced to abruptly pull out of the film. She has since been replaced by Katherine Heigl.

Berry, 44, who has a nanny, currently shares custody of Nahla with Aubry. She pulled out of the New Line production not because she wouldn't have childcare help but because she was concerned about leaving Nahla in L.A. while she filmed in N.Y.C., claims the source.

"When Gabriel refused to go, that became a factor in her decision to pull out of the film because she didn't feel right leaving Nahla," says the source. "No job is that important to Halle. Nahla comes first."

The bitter custody battle is a far cry from the exes' arrangement of only last summer, when Aubry accompanied Berry and Nahla to South Africa while the Oscar winner filmed her upcoming thriller, Dark Tide.

Halle Berry and daughter Nahla

On Monday, Berry's rep issued a statement to PEOPLE, stating that the actress had dropped out of New Year's Eve to focus on her "serious concerns" about Nahla's well-being while in Aubry's care.

The next day, Aubry, 35, countered with his own statement, in which he alluded to her withdrawal from New Year's Eve. "While Gabriel is disappointed in Halle's decision to falsely malign him publicly and for her own purposes, he refuses to be pulled into her dispute over a canceled film production," a rep for the model stated.

 Reporting by JULIE JORDAN, ELIZABETH LEONARD, OLIVER JONES

For much more on Halle and Gabriel's custody battle, pick up this week's issue of PEOPLE, on newsstands now